The present invention relates to diagnostics of equipment used with industrial processes. More specifically, the invention relates to process devices which perform diagnostics.
Process devices are used in industrial process control systems to control, measure or monitor a process. A control device is a process device which is used to control the process and includes pumps, valves, actuators, solenoids, motors, mixers, agitators, breaker, crusher, roller, mill, ball mill, kneader, blender, filter, cyclone, centrifuge, tower, dryer, conveyor, separator, elevator, hoist, heater, cooler or others. A valve controller includes a valve actuator coupled to a valve used to control flow of process fluid. A pump controller includes a motor controller or actuator coupled to a pump. Other process devices include transmitters which may measure physical parameters such as pressure, temperature, flow, etc. Diagnostics of process devices can be used to identify a failed process device or predict an impending failure in the device or another process component.
Vibration of process equipment such as process piping is disruptive to industrial processes and can result in damage to the piping, instrumentation, and other components of the industrial plant. For example, during normal operation of the process, vibration arises through various sources. The vibration is transmitted to the components which are used in the process. Over extended time, these vibrations can cause degradation in the performance of the components and eventual failure of the components.
Sensing vibrations is a known method used to diagnose process devices. A vibration sensor such as an accelerometer placed directly on a process device can be used to sense vibration noise signals generated by the device. Vibrations are isolated and evaluated by identifying those which exceed an amplitude threshold or which have an abnormal frequency which are indicative of an actual or impending failure or reduction of performance. For example, sensors are placed on pump or motor housings, discharge valves, or flanges associated with the process device. Another known diagnostic method is a manual inspection in which an operator listens for abnormal sounds from the control device.
Detecting harmful vibrations can allow damaged process equipment to be replaced prior to its ultimate failure. Similarly, the vibrations can be used to detect aberrations in operation of equipment or to compensate for degradation in components of the equipment. There is an ongoing need for improved diagnostic technology in industrial process control and monitoring for detecting failed components and components which have been degraded or are in the process of failing. One such technique is shown in U.S. Pat. No. 6,601,005, issued Jul. 29, 2003 and entitled PROCESS DEVICE DIAGNOSTICS USING PROCESS VARIABLE SENSOR SIGNAL which is incorporated herein by reference.